This project describes the application of quantitative neuroimaging and neurophysiological techniques to the study of the AIDS dementia complex (ADC). FDG/PET, spin-echo MRI and quantitative EEG/event-related potentials (ERP's) will be employed to investigate the pathophysiology of the neuropsychiatric symptoms of ADC and the nature and evolution of subcortical dementia. Using FDG/PET, we plan to confirm and extend our previous finding of relative subcortical hypermetabolism early in the course of ADC, and to define metabolic covariance patterns that provide sensitive, quantitative indices of disease severity and progression. Since quantitative MRI measures of CSF volume may be more sensitive to the presence of HIV infection than subjective atrophy ratings, and having developed and validated a quantitative MRI method for analyzing serial MRI scans obtained from normal volunteer subjects, we propose to use well-characterized MRI techniques to evaluate -- in cross-sectional and longitudinal studies of asymptomatic and mildly symptomatic seropositives -- the diagnostic and prognostic value of serial measurements of CSF, gray-matter and white-matter compartmental volumes. Finally, standard electrophysiologic measures (EEG power and ERP latency) obtained during FDG/PET imaging will be correlated with clinical, neurobehavioral and metabolic indices of disease severity in an effort to assess the potential of surface EEG recording for ADC diagnosis and staging.